Modular fresnel solar energy collection system

ABSTRACT

A modular linear Fresnel solar energy collection system comprises one or more reflector units having a number of spaced, elongated solar panels that extend between a pair of opposed, light-weight aluminum beams. A first drive mechanism rotates the solar panels at angles progressively increasing from the center of the two beams to their ends so that each panel reflects incident sunlight to a secondary reflector located above the panels. The secondary reflector, in turn, reflects the sunlight it receives from the solar panels onto a receiver tube mounted in a fixed position substantially concentric to a central axis extending between the two aluminum beams. A second drive mechanism is coupled to one of the beams which is operative to pivot the assembly of beams, solar panels and secondary reflector between a generally easterly direction and westerly direction in order to track the apparent movement of the sun during the course of a day.

FIELD OF THE INVENTION

This invention relates to the generation of electrical energy through solar thermal power collection, and, more particularly, to a modular Fresnel solar energy collection system that employs a secondary reflector, light-weight solar panels and a fixed linear receiver through which a heat transfer fluid is circulated.

BACKGROUND OF THE INVENTION

Systems for the generation of electricity by collecting solar thermal radiation were first introduced in 1914, and have become increasingly popular with the rise in fossil fuel costs and concerns over global warming. A majority of solar energy collection systems currently in use employ parabolic, trough-shaped reflectors that focus the sun's energy on a receiver such as an engine. Recently, a new type of system has emerged known as a linear Fresnel reflector that includes a series of long, narrow mirrors having a shallow curvature, or none at all, which focus light onto one or more linear receivers positioned above the mirrors. The concept of large reflectors being broken down into many Fresnel sub-elements to improve manageability was advanced by Baum et al. (1957), and in the 1960's, important development work was undertaken by the solar pioneer Giovanni Francia (Francia, 1968) of the University of Genoa, who developed both linear Fresnel reflector systems and Fresnel point focus systems. Typically, a linear Fresnel reflector focuses sunlight at 80 to 100 times its normal intensity on the receiver. The concentrated energy heats a heat transfer fluid flowing through the receiver, which, in turn, is used to generate steam to power a turbine that drives an electric generator.

Instead of a large parabolic surface, Fresnel reflectors use many smaller mirrors which are more manageable, easier to install, less expensive to maintain and aim to reduce overall costs by sharing a receiver between several mirrors while still using simple line-focus geometry with one axis of tracking, i.e., the individual mirrors can pivot in a generally easterly and westerly direction. Despite these advantages, there is more heat loss due to the larger width dimension of the receiver which is needed to compensate for the lack of curvature in the mirrors. Another disadvantage of current linear Fresnel reflectors is that although they work well when the sun is nearly vertical in the sky, e.g. between about 10:00 a.m. to 2:00 p.m., rapid performance degradation occurs at other times during the day. As the sun incident angle increases, the solar collection efficiency drops quickly because while the mirrors are pivotal, the framework supporting them is stationary.

The goal of any solar collection system is to reduce the cost of electricity generated. There are fundamentally two ways to do this, namely, reduce the cost of the solar field and annual operating expenses, and, to increase system efficiency. Solar field optical efficiency is dependent upon a number of factors, including, without limitation, sunlight incident angle effects, collector tracking error, the geometric accuracy of the mirrors to focus light on the receiver tubes, mirror reflectivity, cleanliness of the mirrors, the creation of shadows across the mirrors, transmittance of solar energy into the receiver tubes, cleanliness of the receiver tubes, absorption of solar energy by the receiver tubes, end losses and the creation of shadows between rows of mirrors. While current systems produce electricity at a cost in the range of $0.12 to $0.18 per kilowatt-hour, it is desirable to achieve a cost level of about $0.05 per kilowatt-hour to be more competitive with present fossil-fuel based systems.

SUMMARY OF THE INVENTION

This invention is directed to a linear Fresnel solar energy collection system that improves solar field efficiency, lowers operational and maintenance costs, and therefore reduces the overall cost of generating electricity per kilowatt-hour.

One aspect of this invention is predicated on the concept providing a simple, modular linear Fresnel solar energy collection system comprising one or more reflector units each fabricated using light-weight materials arranged in a construction that is highly accessible, easily maintained, and lower in initial cost. In one embodiment, each reflector unit comprises a number of spaced, elongated solar panels, having a slightly curved or flat reflective surface, that extend between a pair of opposed, light-weight aluminum beams. A first drive mechanism rotates the solar panels at angles progressively increasing from the center of the two beams to their ends so that each panel reflects incident sunlight to a secondary reflector located above the panels. The secondary reflector, in turn, reflects the sunlight it receives from the solar panels onto a receiver tube mounted in a fixed position substantially concentric to a central axis extending between the two aluminum beams. A second drive mechanism is coupled to one of the beams which is operative to pivot the assembly of beams, solar panels and secondary reflector between a generally easterly direction and westerly direction in order to track the apparent movement of the sun during the course of a day.

Preferably, each solar panel comprises a honeycomb aluminum section and a highly reflective silver-metallized surface connected together by an adhesive layer. The solar panels are strong, durable, light-weight and efficiently reflect incident sunlight many times its normal intensity onto the secondary reflector. The reflective surface of such panels may be washed to maintain cleanliness which enhances the efficiency with which they reflect incident sunlight to the secondary reflector.

A heat transfer fluid is circulated through the receiver tube for heating by the sunlight directed thereto from the secondary reflector. Because the receiver tube is fixed relative to the pivoting beams, it may be connected to a fixed transfer conduit that communicates with a steam generator and turbine. Since both the receiver tube and transfer conduit are mounted in a fixed position, heat losses resulting from the transfer of fluid out of the receiver tube are minimized and maintenance problems are reduced.

In an alternative embodiment, a reflector unit includes solar panels that are formed in smaller segments and mounted to a number of shafts extending between the opposed beams described above. The shafts are operative to tilt the segmented solar panels at a desired latitude angle, e.g. in a generally northerly or southerly direction, dependent upon the geographic location of the system. This allows the system of this invention to account for the varying incidence angle of the sun with the earth as the seasons change so that the solar panels more directly face the sun throughout the year. An improvement in solar collection efficiency of at least 5% may be realized by this enhancement of the present invention.

The several embodiments of this invention are modular in construction in the sense that several reflector units may be mounted side-by-side, and their receiver tubes connected, to form a linear Fresnel solar collection system with increased capacity and overall efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure, operation and advantages of the presently preferred embodiment of this invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of one embodiment of a reflector unit employed in the Fresnel solar energy collection system of this invention;

FIG. 2 is a perspective view of a solar panel of this invention;

FIG. 3 is an enlarged, partially disassembled view of the encircled portion of the solar panel depicted in FIG. 2;

FIG. 4 is a perspective view of the receiver tube employed in the system herein;

FIG. 5 is a schematic, end view of the solar panels and secondary reflector of the system depicted in FIG. 1, illustrating the angular orientation of the solar panels;

FIG. 6 is a schematic view of one embodiment of a first drive mechanism for tilting a solar panel at an angle such as depicted in FIG. 5;

FIG. 7 is a schematic view of an alternative embodiment of a first drive mechanism for tilting a number of solar panels at the same time;

FIG. 8 is a perspective view of a second drive mechanism for collectively pivoting the beams, solar panels and secondary reflector;

FIG. 9 is an end view of the second drive mechanism illustrated in FIG. 8;

FIG. 10 is a perspective view of a solar collection system according to this invention in which a number of reflector units shown in FIG. 1 are oriented side-by-side;

FIG. 11 is a perspective view of an alternative embodiment of the solar collection system of this invention wherein the opposed beams, solar panels and secondary reflector are not collectively pivotal;

FIG. 12 is a perspective view of the solar panels and beams of an alternative embodiment of a solar energy collection system according to this invention;

FIG. 13 is an enlarged, side view of a portion of FIG. 12 illustrating the manner in which solar panels are mounted on a shaft for tilting movement relative to the opposed beams; and

FIG. 14 is a view similar to FIG. 15 showing solar panels tilted after rotation of the shaft.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, one embodiment of a reflector unit 10 for the solar energy collection system 12 of this invention is illustrated with reference to FIGS. 1-10. The unit 10 is initially generally described, followed by a discussion of individual aspects of the design. Finally, an alternative embodiment of a solar energy collection system according to this invention is discussed with reference to FIG. 12-14.

With reference initially to FIG. 1, the reflector unit 10 comprises a pair of opposed beams 14 and 16, preferably formed of a light-weight, durable and weather resistant material such as aluminum. The beams 14, 16 may be reinforced by a truss structure 18, a portion of which is shown in FIGS. 1 and 8, that is also preferably formed of aluminum or similar material. The beams 14, 16 are spanned by a number of elongated solar panels 20 which are separated from one another so that there is at least some spacing between the side edges of adjacent panels 20. The solar panels 20 pivot relative to the beams 14, 16, in a manner described below. A secondary reflector 22 is located above the solar panels 20, as discussed below, and is supported in that position at each end by rods 23 extending from the beams 14, 16 and truss structure 18. The solar panels 20 and secondary reflector 22 collectively form structure for receiving incident sunlight and reflecting it onto a receiver tube 24 within which a heat transfer fluid is circulated for heating by the sunlight. The receiver tube 24 is preferably located in a fixed position at an axis substantially coincident with the centerline 26 of the two beams 14, 16. See FIG. 5.

The reflector unit 10 may be supported above ground level by pylons 28 secured on a foundation such as concrete footers (not shown) that can support the weight of the unit 10 and wind loading applied to it. As described in detail below, in one embodiment the beams 14, 16, solar panels 20 and secondary reflector 22 may be collectively tilted by operation of a first drive mechanism in a generally easterly and westerly direction.

Referring now to FIGS. 2 and 3, a solar panel 20 according to this invention is shown in greater detail. Each solar panel 20 is generally rectangular in shape having opposed side edges 30 and 32. The panels 20 have a slight concave curvature in a direction from one side edge 30 to the other side edge 32, which may be slightly different from one panel 20 to another as described below. Each panel 20 comprises a base section 34, a top section 36 and an intermediate section 38 sandwiched between the sections 34, 36. The base section 34 is preferably formed of a honeycomb aluminum, or similar light-weight, weather resistant and durable material that may be bent in the slight curvature noted above and shown in FIG. 2. The top section 36 is preferably a highly-reflective, silver-metallized film comprising multiple layers of polymer film with an inner layer of pure silver to provide a reflective surface 40 having high specular reflectance. One suitable material for top section 36 is commercially available from ReflecTech, Inc. of Wheat Ridge, Colo. under the trademark “ReflecTech” solar film. The intermediate layer 38 is preferably a layer of pressure sensitive adhesive. Layer 38 may be affixed on one side to the top section 36 and include a peel-off backing (not shown) which is removed prior to attachment to the base section 34. In one presently preferred embodiment, the solar panels 20 have a length dimension of about 4064 mm, a width dimension of about 460 mm and a thickness of about 25 mm.

The receiver tube 24 is a component employed in prior art solar collection systems and is readily commercially available. As shown in FIG. 4, it comprises a stainless steel housing 42 having a solar-selective absorber surface surrounded by an anti-reflective, evacuated glass sleeve 44. Typically, the housing 42 has a length of 4 meters and a diameter of 70 mm, and the glass sleeve 44 is 115 mm in diameter. A heat transfer fluid such as oil or water is circulated through the housing 42 where it is heated by reflected sunlight, as discussed below. The receiver tube 24 has glass-to-metal seals and metal bellows (not shown) to accommodate differing rates of thermal expansion between the stainless steel housing 42 and glass sleeve 44, and to help maintain the vacuum-tight enclosure. This reduces heat losses at high operating temperatures and protects the solar-select absorber surface of the housing 42 from oxidation.

As noted above, the solar panels 20 and secondary reflector 22 collectively function to direct incident sunlight onto the receiver tube 24 to elevate the temperature of heat transfer fluid circulating within the receiver tube 24 to a level sufficient to operate a steam generator (not shown) for the production of electricity. The positioning of the solar panels 20 with respect to the secondary reflector 22, and the configuration of the solar panels 20 and secondary reflector 22, are both important in maximizing the efficiency of the reflector unit 10. The discussion that follows concerns this aspect of the present invention.

A parabola is a geometric shape defined by the locus of points that are equidistant from a point (the focus) and a line (directrix) that lie in the same plane. Reflective surfaces having the shape of a parabola have been commonly used in solar power collection systems because incident sunlight may be reflected to a collection device located at the focus or directrix of the parabola. The unit 10 of the present invention is designed to tale advantage of this property of a parabola, but in a much more efficient, less expensive and practical manner than taught in the prior art.

The standard mathematical equation defining a parabola is as follows:

Where:

y=x ²/4f

f=the focal point

x=horizontal distance from the center

y=vertical distance

In the presently preferred embodiment of reflector unit 10, each of the solar panels 20 is formed with a curvature according to the above equation. The parabolic effect of focusing rays of light to a focus or directrix of the parabola, discussed above, can be used in a linear arrangement. As viewed in FIG. 5, the beam 14 is shown with the receiver tube 24 depicted within an opening 46 formed in the beam 14, substantially concentric to a centerline 26 of the two beams 14, 16, and the secondary reflector 22 is located at a position spaced from the receiver tube 24. A first array 50 of solar panels 20 extends from the receiver tube 24 to one end of the beams 14, 16, and a second array 52 of solar panels 20 extends from the receiver tube 24 to the opposite end of beams 14, 16. The solar panels 20 within the two arrays 50, 52, each having a parabolic cross section as noted above, are oriented at an angle relative to the secondary reflector 22 such that incident sunlight is reflected onto a focal line 54 or directrix coincident with the secondary reflector 24. This ensures an efficient transfer of thermal energy from the solar panels 20 to the secondary reflector 24.

The manner in which the solar panels 20 may be oriented at the appropriate angles depicted in FIG. 5, is illustrated with reference to FIGS. 6 and 7. One embodiment of a first drive mechanism according to this invention is illustrated in FIG. 6. An end of each a solar panel 20 is fixed within a slot 56 of a mounting fixture 58 which is coupled to the output 60 of a torque motor 62 mounted to the beam 16. The opposite end of panel 20 is pivotally mounted to beam 14. In response to operation of the motor 62, the fixture 58 rotates causing the solar panel 20 it supports to tilt at an angle relative to the secondary reflector 22.

An alternative embodiment of the first drive mechanism of this invention is shown in FIG. 7 wherein a number of solar panels 20 may be rotated at the same time. One end of each panels 20 is mounted to a shaft 64 protruding from one of the beams 14, 16. Each shaft 64, in turn, mounts a follower gear 66. A worm gear 68 having external threads 70 is drivingly connected to each of the follower gears 66 such that rotation of the worm gear 68 causes the follower gears 56 to rotate thus tilting the solar panels 20. In order to tilt the solar panels 20 at different angles relative to the secondary reflector 22, as seen in FIG. 5, the diameter of the follower gear 66 associated with each panel 20 may vary such that the same extent of rotation of the worm gear 68 results in a different amount of rotation of each follower gear 66, and, therefore, a lesser or greater tilting of the respective solar panel 20.

As noted above with reference to FIG. 5, the first and second arrays 50, 52 of solar panels 20 reflect incident light to a directrix 54. The secondary reflector 22 is located along the directrix 54 and is constructed to reflect the light received from solar panels 20 onto the receiver tube 24 to elevate the temperature of heat transfer fluid circulating therein. In one presently preferred embodiment, the secondary reflector 22 is approximately 200 mm to 250 mm in width with a reflective surface 72 in the shape of a hyperbola. The exact geometry of the reflective surface 72 is derived from the Cassegrain Equations for a primary parabolic-shaped reflective surface, which, in this instance, is the parabolic-shaped reflective surface of each solar panel 20, and a secondary hyperboloid reflective surface. The secondary reflector 22 may be constructed of a honeycomb panel having the appropriate hyperboloid shape noted above connected by an adhesive layer to the same material that forms the top section 36 of solar panels 20.

Referring now to FIGS. 8 and 9, it is advantageous for the solar panels 20 to be track the position of the sun throughout the course of a day in order to maximize the efficiency with which the sunlight is reflected to the secondary reflector 22, and, in turn, to the receiver tube 24. In the presently preferred embodiment of this invention, a second drive mechanism is provided for collectively pivoting the beams 14, 16, solar panels 20 and secondary reflector 24 at an angle of at least about +/−30° relative to horizontal. This limited rotation improves the solar energy collection in the early hours of day and late in the afternoon by tilting the solar panels 20 toward the sun. However, by limiting the rotation angle lower height pylons 28 may be used and the spacing required between rows of panels 20 may be reduced to avoid shadowing. This second drive mechanism comprises a support frame 74 connected to a pylon 28 which rotatably mounts three rollers 76, 78 and 80 spaced approximately 120° apart. These rollers 76-80 receive and support a drive wheel 82 which is connected by a link chain 84, or other suitable drive means such as a belt, to the output shaft of a motor 86. The drive wheel 82 is connected by a plate 88 to the rods 23 which support the secondary reflector 22 at one end, and connect to the beams 14, 16 and truss structure 18 at the opposite end. In response to operation of the motor 86, the drive wheel 82 rotates with respect to the rollers 76-80. The rods 23 and beams 14, 16 rotate with the drive wheel 82, thus pivoting relative to the pylons 28.

In the presently preferred embodiment, the receiver tube 24 remains in a fixed position with respect to the beams 14, 16 and drive wheel 82 throughout the pivotal motion of the beams 14, 16, solar panels 20 and secondary reflector 22. As described above, the receiver tube 24 may extend through an openings 46 formed in each beam 14, 16. A protruding end of receiver tube 24 enters a bore 90 formed in the plate 88, and a central bore 92 formed in the drive wheel 82 where it is received and supported by a bearing 94 that allows the receiver tube 24 to remain in a fixed position during rotation of the drive wheel 82. This construction has the advantage of allowing the receiver tube 24 to be connected to a fixed transfer conduit coupled to a steam generator (not shown). Consequently, the expensive and leak-prone connections between the moving receiver tubes and transfer conduits employed in some prior art systems are eliminated in this invention.

The solar energy collection system 12 of this invention is modular in construction. As shown in FIG. 10, a number of individual reflector units 10 depicted in FIG. 1 and described above may be located side-by-side to increase capacity and overall efficiency of the solar field. In such arrangements, a second drive mechanism of the type described above in connection with a discussion of FIGS. 8 and 9 may be located in between adjacent units 10 such that each end of the output shaft of motor 86 may be coupled to the drive wheel 82 of one of the units 10 in the manner described above. Further, the receiver tube 24 of one unit 10 may be coupled to the receiver tube 24 of an adjacent unit 10 to transmit heat transfer fluid to one or more conduits (not shown) for the combined collection system.

As discussed above with reference to FIGS. 8-10, the reflector units 10 of this invention may be provided with a second drive mechanism to collectively tilt the beams 14, 16, solar panels 20 and secondary reflector 22 to track the position of the sun. In an alternative embodiment shown in FIG. 11, the same reflector units 10 described above and shown in FIG. 1 are employed but in a solar collection system 95 in which the units 10 are secured in a fixed position, side-by-side, to supports posts 96. The individual panels 20 within each unit 10 of the system in FIG. 11 pivot as described above, but the beams 14, 16 are held in a fixed position to the posts 96. The receive tubes 24 of adjacent units 10 may be connected to one another, as in the embodiment of FIGS. 8-10.

A still further embodiment of a solar energy collection system according to this invention having one or more reflector units 100 is illustrated in FIGS. 12-14. The reflector units 100 are similar to units 10 in many respects except for structure that permits adjustment of the position. of solar panels about a second axis. As discussed above, individual solar panels 20, as well as the entire assembly of the beams 14, 16, panels 20 and secondary reflector 22, may be pivoted relative an axis generally coincident with the centerline 26 of the beams 14, 16. Such motion is in an easterly to westerly direction consistent with the apparent movement of the sun across the sky during the daylight hours. As is well known, the earth tilts on its axis during the course of a year causing the change of seasons and altering the angle of inclination of the sun's rays. The unit 100 of this embodiment is designed to not only track the sun's daily path but its annual inclination.

The same beams 14, 16 described above are employed in unit 100, but instead of elongated solar panels 20 extending between the two beams 14, 16, a plurality of shorter, segmented solar panels 102 are provided. The solar panels 102 are divided into groups, and each group of panels 102 essentially takes the place of a single solar panel 20 in the embodiment of FIGS. 1-11. As best seen in FIG. 12, one group of several panels 100 is mounted within each of a number of sub-frames 104, e.g. a generally rectangular-shaped structure having opposed ends and opposed sides. One end of each sub-frame 104 is pivotally mounted to one of the beams 14 or 16, and the opposite end thereof is connected to a mounting fixture (not shown) secured to the other beam 14 or 16, such as the fixture 58 described above in connection with a discussion of FIG. 6. The sub-frames 104 are pivoted relative to the beams 14, 16 by operation of torque motors, such as motors 62, at the same angles relative to the secondary reflector 22 as solar panels 20 described above. See FIGS. 5 and 6.

In one embodiment, as shown in FIGS. 13 and 14, the panels 100 within each group may be coupled to a threaded shaft 106, which, in turn, is rotatably mounted to the end walls of a sub-frame 104. A lever arm 108 may extend from each panel 100 and connect to an internally threaded sleeve 110 which threads onto the shaft 106. In response to rotation of the shafts 106, either manually by turning a knob 112 or by operation of a motor (not shown), the sleeves 110 move axially along the shafts 106 causing the panels 124 to tilt. The direction of rotation of the shaft 106 determines the direction of tilting of the panels 100. In this manner, the panels 100 may be tilted in a northerly direction or a southerly direction according the angle of inclination of the sun. The remainder of the structure and operation of the solar collection system depicted in FIGS. 12-14 is essentially the same as that described above in connection with a discussion of the system shown in FIG. 10.

While the invention has been described with reference to a preferred embodiment, it should be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof.

For example, the receiver tube 24 is depicted in FIGS. 5, 11 and 12 as being positioned at the center of the beams 14 and 16 and substantially concentric to the centerline 26. As shown in FIGS. 1, 8 and 10, the receiver tube 24 may also be located slightly above the center of the beams 14, 16. In both instances, the receiver tube 24 is located substantially at the center of rotation of the beams 14, 16 and generally at the center of gravity of the reflector units 10 or 100.

Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A solar energy collection system, comprising: a first beam and a second beam; a number of solar panels each having a reflective surface, said solar panels extending between said first and second beams; at least one drive mechanism coupled to said solar panels and being operative to tilt respective solar panels into a position to reflect sunlight on said reflective surface thereof; a receiver tube within which a heat transfer fluid is circulated; a secondary reflector positioned so as to receive sunlight reflective from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 2. The system of claim 1 in which said at least one drive mechanism comprises a number of drive mechanisms each including a motor having an output coupled to one end of a solar panel, said motors being operative to pivot a respective solar panel at an angle relative to said secondary reflector.
 3. The system of claim 2 in which each of said drive mechanisms operates independent of the other.
 4. The system of claim 1 in which said at least one drive mechanism comprises a worm gear drivingly connected to a number of follower gears each coupled to one of said solar panels, said worm gear being operative to rotate said follower gears to tilt respective solar panels relative to said secondary reflector.
 5. A solar energy collector system, comprising: a first beam and a second beam; a number of solar panels, each of said solar panels including a first section formed of a light-weight honeycomb structure, a second section having a reflective surface and a third section connecting said first and second layers, said solar panels extending between said first and second beams; at least one drive mechanism coupled to said solar panels and being operative to tilt respective solar panels into a position to reflect sunlight on said reflective surface thereof; a receiver tube within which a heat transfer fluid is circulated; a secondary reflector positioned so as to receive sunlight reflected from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 6. The system of claim 5 in which said light-weight honeycomb structure is honeycomb aluminum.
 7. The system of claim 5 in which said first section has opposed sides, said first section being formed in a concave shape between said opposed sides.
 8. A solar energy collection system, comprising: a first beam and a second beam; a number of solar panels each having a reflective surface, said solar panels extending between said first and second beams; a first drive mechanism coupled to said solar panels and being operative to tilt respective solar panels into a position to reflect sunlight on said reflective surface thereof; a second drive mechanism operative to pivot said first and second beams between a first position in which said solar panels face a generally easterly direction, and second position in which said solar panels face a generally westerly direction; a receiver tube within which a heat transfer fluid is circulated; a secondary reflector positioned so as to receive sunlight reflected from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 9. The system of claim 8 in which said at least one first drive mechanism comprises a number of drive mechanisms each including a motor having an output coupled to one end of a solar panel, said motors being operative to pivot a respective solar panel at an angle relative to said secondary reflector.
 10. The system of claim 8 in which said at least one first drive mechanism comprises a worm gear drivingly connected to a number of follower gears each coupled to one of said solar panels, said worm gear being operative to rotate said follower gears to tilt respective solar panels relative to said secondary reflector.
 11. A solar energy collection system, comprising: a first beam and a second beam; a number of solar panels each having a reflective surface, said solar panels extending between said first and second beams; a first drive mechanism operative to pivot said first and second beams between a first position in which said solar panels face a generally easterly direction, and second position in which said solar panels face a generally westerly direction; a number of second drive mechanisms coupled to at least one of said first and second beams, each of said second drive mechanisms mounting a group of said solar panels and being operative to tilt said solar panels within a respective group in a generally northerly direction and in a generally southerly direction to reflect sunlight incident on said reflective surface thereof; a receiver tube within which a heat transfer fluid is circulated; a secondary reflector positioned so as to receive sunlight reflective from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 12. The system of claim 11 in which each of said solar panels comprises a first section formed of a light-weight honeycomb structure, a second section having a reflective surface and a third section connecting said first and second layers.
 13. The system of claim 11 in which said light-weight honeycomb structure is honeycomb aluminum.
 14. The system of claim 11 in which said first section has opposed sides, said first section being formed in a concave shape between said opposed sides.
 15. A solar energy collector system, comprising: a number of reflector units oriented side-by-side, each of said reflector units comprising: (i) a first beam and a second beam; (ii) a number of solar panels each having a reflective surface, said solar panels extending between said first and second beams; (iii) at least one first drive mechanism coupled to said solar panels and being operative to tilt respective solar panels into a position to reflect sunlight on said reflective surface thereof; (iv) a receiver tube within which a heat transfer fluid is circulated; (v) a secondary reflector positioned so as to receive sunlight reflected from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 16. The system of claim 15 in which said at least one first drive mechanism of each reflector units comprises a number of drive mechanisms each including a motor having an output coupled to one end of a solar panel, said motors being operative to pivot a respective solar panel at an angle relative to said secondary reflector.
 17. The system of claim 15 in which said at least one first drive mechanism of each of said reflector units is operative to tilt each of said solar panels individually, each of said reflector units further including a second drive mechanism operative to pivot said first and second beams in an easterly direction and in a westerly direction.
 18. The system of claim 15 in which said solar panels of each reflector unit comprises a first section formed of a light-weight honeycomb structure, a second section having a reflective surface and a third section connecting said first and second layers.
 19. The system of claim 18 in which said light-weight honeycomb structure is honeycomb aluminum.
 20. The system of claim 18 in which said first section has opposed sides, said first section being formed in a concave shape between said opposed sides.
 21. A solar energy collector system, comprising: a number of reflector units oriented side-by-side, each of said reflect units comprising: (i) a first beam and a second beam; (ii) a number of solar panels each having a reflective surface, said solar panels extending between said first and second beams; (iii) a first drive mechanism operative to pivot said first and second beams between a first position in which said solar panels face a generally easterly direction, and second position in which said solar panels face a generally westerly direction; (iv) a number of second drive mechanisms each mounting a group of said solar panels and being operative to tilt said solar panels within a respective group in a generally northerly direction and in a generally southerly direction to reflect sunlight incident on said reflective surface thereof; (v) a receiver tube within which a heat transfer fluid is circulated; (vi) a secondary reflector positioned so as to receive sunlight reflected from said solar panels and to reflect said sunlight onto said receiver tube to heat the heat transfer fluid therein.
 22. The system of claim 21 in which said solar panels of each reflector unit comprises a first section formed of a light-weight honeycomb structure, a second section having a reflective surface and a third section connecting said first and second layers.
 23. The system of claim 22 in which said light-weight honeycomb structure is honeycomb aluminum.
 24. The system of claim 22 in which said first section has opposed sides, said first section being formed in a concave shape between said opposed sides. 